Crude oil products are globally obtained from subterranean reservoirs using techniques such as drilling and hydraulic fracturing. Transportation of crude oil products from the subterranean reservoir is accomplished by moving and storing the crude oil products in a series of containments, including pipes, pumps, holding tanks, processing tanks, storage tanks, and containers suitable for air, road, or ocean transportation. During such moving and/or storage, the crude oil product is often subjected to ambient temperatures between −40° C. and 60° C.
Crude oil products include linear and branched alkanes having the general formula CnH2n+2 wherein n is typically about 1-50, although minor amounts of longer hydrocarbon chains do occur. The higher molecular weight alkanes can be problematic in that their melting points tend to be greater than ambient temperatures in some cases. For example, nonadecane has a melting point of 33° C.; higher alkanes can have melting points in excess of 60° C.
The high melting alkane fractions present in crude oil products can cause formation of paraffinic residue that solidifies and deposits on containments used to transport and store crude oil. The solidified residue, also known as “paraffin”, not only reduces the effective volume of the structure it's contained within but also represents a loss of a valuable component from the body of the crude oil. Excessive paraffin wax buildup reduces the efficiency of transporting crude oil and leads to increased costs related to added downtime for cleaning of the pipes and/or vessels as well as disposal of residues removed from the vessel which increase environmental burden. While the pipelines and vessels can be cleaned to remove the paraffinic residue, the process generates hazardous waste, takes the vessel out of service during the cleaning period, and is expensive.
The formation of paraffin wax can be reduced by conventional additives, called “paraffin inhibitors” (PI) which interfere with the crystallization process of wax and/or suspend wax crystals in the oil. The addition of PI to the crude oil is effective in dispersing the paraffinic residue, thereby reducing the formation of residues in the pipelines and vessels to the benefit of the oil and gas industry. The PI effectively reduce the formation of paraffinic residues during storage and transportation of the crude oil products.
Typical PI are polymers such as e.g. ethylene polymers and copolymers thereof with vinyl acetate, acrylonitrile, or α-olefins such as octene, butene, propylene, and the like; comb polymers with alkyl side chains such as methacrylate ester copolymers, maleic-olefinic ester copolymers, and maleic-olefinic amide copolymers; and branched copolymers having alkyl side chains such as alkylphenol-formaldehyde copolymers and polyethyleneimines.
In order to inhibit paraffin formation a conventional PI must be present within the crude oil itself. That is, conventional PIs are dissolved or dispersed within the crude oil in every instance where it will be contacted with a containment surface. For a continuous flow of crude oil through oil recovery containments such as pipes, therefore, PI must be continuously added. The use of PI increases the material cost of the production stream overall, since it must be added to each aliquot of crude oil that is transported. Additionally, the concentration of the PI in the oil must be continuously monitored and adjusted as it flows from the subterranean reservoir and through or into one or more containments: too low a concentration will result in paraffin deposition; too high a concentration adds to cost without receiving benefit and potentially interferes with the desired actions of one or more other additives also present in the crude oil (corrosion inhibitors, demulsifiers, anti-scaling agents, and the like).
Finally, severe dispensing and usage problems are associated with the use of paraffin inhibitor concentrates in areas where the winter temperature goes well below 0° C. Concentrated formulations of PI in organic solvents are used to provide a pumpable or pourable liquid format for delivery of the PI. However, the polymeric compounds employed as PI tend to solidify at temperatures at or below about 0° C. In such temperatures, the concentrates tend to form gels or even solids with decreasing temperature, leading to severe issues with pumping or pouring the concentrates to affect delivery thereof to the crude oil stream.
There is a need in the industry to overcome the aforementioned issues with conventional paraffin inhibitors.